1. Field of the Invention
The present invention concerns the field of gas turbines. It concerns a method for igniting the combustion chamber of a gas turbine unit and an ignition device for carrying out the method.
2. Brief Description of the Related Art
The continuous combustion in the combustion chamber of a gas turbine is initiated when an external ignition source ignites the combustion mixture (usually an air/fuel mixture). Usually this is accomplished with electric sparks that ignite the mixture in the combustion chamber either directly or indirectly using a so-called pilot burner. Alternative ignition sources provide the required energy via a glowing surface or a laser light source. The ignition plug for generating the ignition spark requires high electric voltage directly in the combustion chamber. The supply line, especially the isolation of this high voltage line that must be comprised of ceramics due to the existing temperatures at the compressor exit, is relatively susceptible to heat expansion and vibrations. This is why such ignition systems are comparatively sensitive and must be replaced relatively often during the life of a gas turbine. This could result in low availability of the unit. The other known ignition by way of an auto-ignition avoids the supply of high voltages; however, the ceramic glow element itself currently does not have a long enough lifecycle.
In a completely different technical field, i.e., in military applications, it is necessary to initiate a chemical reaction with very simple, robust devices. This led to the development of so-called Resonance Igniters that utilize the heating of gas for ignition purposes with the gas supercritically dissipating its pressure energy into heat in a resonance tube. Usually solid reaction mixtures or—using a H2/O2 and/or H2/air ignition flame—other fuels are being ignited (ref. for example U.S. Pat. Nos. 3,994,232 or 5,109,669).